Describe the system arrangement and explain the function and operation of a typical passanger and crew oxygen?
Answers:
Crew Oxygen
This is situated at all crew seats. It is usually a 2 litre per minute (lpm) or 4(lpm) system. They are oxygen tanks that can be worn to allow the crew to move around after the emergency descent to 10,000feet approx.
Pax Oxygen
These are in the Overhead consoles in the form of small gaseous oxygen botttles. They are fired by pulling the masks. They last for 12 minutes which is enough for the aircraft to regain normal flight at 10,000feet. There are four masks per row in a 3-3 type aircraft. This is for babies and crew who may be in the aisle. There are usually two in the toilets incase of mothers with babies or mile high club members. There are also drop down masks in the Galleys for the crew if it is a sudden decompression.
Flight Deck Oxygen.
They have an on demand oxygen system. This gives them 100% oxygen saturation. It is delivered by a mask which inflates and fits around the head. It can be worn on its own or with goggles in case of contamination in the Flight deck. The pilort and passenger oxygen systems are completely seperate. The pax one is a gaseous reaction and the pilots is pure air.
It's no use asking us lot
The oxygen is normally configured to match the number of seats per row. For example if an aircraft had 3 seats on each side of the aisle then there would normally be four masks above each row. The extra one is for a child if sat on a parents knee. There are exceptions to this as a lot of aircraft have different configurations. The reason they are on is us humans are not very good when it comes it breathing at high altitudes so we need help. Aircraft cabins are pressurised to between 7000 feet and 8000 feet. We are fine at this but when it gets any higher then we find it hard to get enough oxygen. The masks will normally drop if the cabin pressure exceeds 14000 feet. Normal passenger aircraft cruise at around 37000 feet - 41000 feet. If we were exposed at the kind of altitude the average person would only remain concious for around 1 minute. Hope that explains it. If not drop me a line and i will try explain it better.
oxygen systems as previously mentioned at pressurised to about 8,000 ft, the main reason for this is that at around 10000ft the atmosphere is so thin that any decompression would result in usable oxygen would give the grew and passangers around 30-45 seconds of conscientiousness, at which time dependent on fitness and whether the individual smokes, most people would start to suffer hypoxia(oxygen deprivation) which results in confusion, hysteria, visual impairment and then unconsciousness, which would prove fatal to the pax and crew.
the emergency system which drops down is a chemical system which provides only 15 minutes of relief.
the crews are trained to descend to below 10000 ft in the first minute otherwise they will lose the aircraft.
hope this helps..
JD
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